Stock transfer between storage locations of same plant

Hi all!

Im just a junior and i need your help.

I want to transfer materials from a storage location to another storage location of same plant. I checked other discussions and tried to do this using MB1B but this Tcode did not help me because i want to keep storage unit numbers. While im using MB1B, the material is sent to 921 - Transfer storage type and when the material is placed 921 im losing storage unit number. I want to keep this number to follow the material moves.

How can i keep the number while im transferring the material between storage locations within same plant ?

Ty for your help.