If I would to explain this scripture and show the Trinity, I would divide it as follows:
And, behold, I am with thee, - This is God the Father. He's the great I AM!
and will keep thee in all places whither thou goest, and will bring thee again into this land; This is God the Son. He said in Matthew that He will be with you alway, even unto the ends of the earth. He came to restore us to our rightful land, back to our Father, the creator.
for I will not leave thee, until I have done that which I have spoken to thee of. - This is God the Holy Spirit. He is our comforter. He's presently with us making us do right when we want to do wrong.