I believe in the Trinity myself, however I was wondering if the Bible implies that one must believe in it as a requirement to attain salvation and if so, what is the minimum acceptable
understanding of it.
Scripture does not present us with a list of theological propositions that one must accept in order to attain salvation, because that isn't what salvation means biblically.
Salvation is the power and work of God--what God has accomplished for us in Jesus. It is an objective act of God to rescue us from sin and death. Right theology affirms the truth of the Gospel and ensures the Gospel is faithfully proclaimed, but having right theology is not a condition for the Gospel itself. That is, it is true that Christ died for us regardless if we understand that properly or not.
For Lutherans, such as myself, we are explicitly clear that salvation is by grace alone through faith alone, in, because, and on account of Christ alone. That means salvation comes from God alone, who gives us faith as pure gift--"For it is by grace that you have been saved, through faith, and this is not of yourselves, it is God's gift; not of works so that none may boast." (Ephesians 2:8-9). Even faith is extra nos, from outside of ourselves, from God alone who gives and creates faith by the power of His word (Romans 10:17).
This means that you don't have to have a Masters of Divinity degree in order to be saved. To be saved you simply have to exist, and when God meets us in Word and Sacrament, He faithfully and graciously acts to work to give and create faith. So even the tiny child and the simple, on account of faith, are indeed saved.
Even the infant can have faith, because faith is not about the power of reason, but is simple trust in Christ granted to us by God the Holy Spirit through the efficacious power of His word.
Now, as we, having been granted faith and now walking in faith through discipleship, being reared up faith--by our parents, by the congregation, through the faithful ministry of the Church. As we grow, and learn, and study, and mature, good theology means faithful preaching. Good theology means we are being raised and taught and discipled in the Church. We are not being led by our noses to various errors which can lead us away from faith. The danger of heresy is not that if we happen to have wrong theological ideas we can't be saved; it's that heresy distorts truth and, therefore, can lead us away from faith in Christ. If one persists in heresy, actively and knowingly, they are making shipwreck of their faith--and the day may come when they no longer believe in Christ at all.
What does this mean? It means that if you were to ask me is it possible that the average Mormon who simply grew up Mormon and doesn't know any better can be saved, the answer to that is I think yes, of course. But we who hold firm to the faith of the Church have an obligation to share with them the better way found in the orthodox and faithful confession that has been held since the beginning. Mormonism is still spiritually dead and contrary to Christ, but can a Mormon be saved in spite of Mormonism because of simple trust in Christ? Of course they can. Salvation is not Divine Gatekeeping, Jesus isn't a bouncer keeping people outside of His sheepfold, but is the Good Shepherd actively herding us into it.
The same is true of other non-Trinitarian groups. It is not intellectual assent or knowledge of the doctrine of the Trinity that saves us; it is Jesus Christ who saves us. What confessing true faith in the Holy Trinity does is keep our heads and hearts in true knowledge of God, and keeps us in faith, by faithfully presenting the truth of the Gospel, of who Jesus is, of who His Father is, who the Holy Spirit is; and what the Three Persons have done and are doing. Of God's love and grace and work. That we might know God and God's love for us in the Gospel. That keeps us in faith, the Holy Spirit does this.
Good theology is not about "getting saved"; but it is about keeping us safe within the sheepfold of faith.
-CryptoLutheran