how can i convert integer to code

i have a table that has a unique field of type integer containing data i imported from SQL server and i want to pull the data into my client ledger entry table but this time assigning the new client numbers to it and in order to do this am comparing in my code that if the old client number is equal to the the client number in the table i imported into the native database then it should assign its corresponding number in the client table into the the client ledger entry table.
i get this error espression type integer cannot be converted to code value
](*,)