Old material number to be saved in field MARA-BISMT

What causes this issue?

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

You decided to save the old field contents for material numbers (that
is, the status before the conversion) in field MARA-BISMT.
Note that the existing data in field MARA-BISMT( coming for example from
data transfer into R/3 ) will be overwritten. Additionally the old
material numbers which are converted because of automatic renaming will
also be saved in MARA-BISMT.

System Response

How to fix this error?

Error message extract from SAP system. Copyright SAP SE.