In the Greek, that's "If there is a natural body."
"The body that is sown is perishable, it is raised imperishable; it is sown in dishonor, it is raised in glory, etc. (1 Corinthians 15:42-43)
Two terms are in play here that Paul uses in a specific way rather than common way, one originating with Paul himself: natural body and spiritual body.
Natural body is the perishable, corrupt, weak, sinful (physical) body. (1 Corinthians 15:50)
Spiritual body is a NT term originating with Paul and used by no one else in the NT epistles.
By this term, Paul means the imperishable, incorruptible (immortal), not-characterized-by-sin physical body (1 Corinthians 15:42-44).
He calls it spiritual in contrast to natural, and not in contrast to physical, material, or corporeal.
Paul doesn't use the word "spiritual" to denote the non-physical, non-material, non-corporeal.
He uses it to denote the realm of spirit, usually the Holy Spirit.
So when Paul speaks of a spiritual body, he is not speaking of a non-physical body, but of the imperishable, incorruptible, sinless physical body of the resurrection, in contrast to the natural body
which is perishable, corrupt, weak, sinful.