If this is pure SAS code only then it's quite strait forward:
SAS is on a code level very backward compatible and the huge majority of code just might run under the new SAS version without any problems.
Migrating from SAS v6 to SAS v9:
Well, that's quite a jump. I believe 99% of code would just work except from a few commands which might no more exists under SAS 9 (i.e: DO OVER).
If there are also SAS datasets involved: Migrating these datasets from the v6 version to the v9 version would be beneficial - but even without migrating everything still would work (also all variable names would be restricted to 8 characters only).
If there is also metadata involved (i.e. EG projects) then the story gets much more complicated and the migration path will depend on the source and target version. For SAS9.1 to SAS9.2: There is a migration wizard for EG projects in the EG folder which can be used - but first all the metadata must be setup in the target and source environment. It's best to read first the SAS docus about migrating from SAS9.1 to SAS9.2 and plan the steps prior to executing them - or you risk to end up with heaps of problems and a "messy" 9.2 environment (speaking from experience....).