You need to compile your code and you'll get (or should get) a section in the COBOL compile output that looks something like this
LINE # HEXLOC VERB LINE # HEXLOC VERB
023835 0098FE IF 023836 00990E SET
023838 00991A SET 023841 00992A PERFORM
023843 009950 PERFORM 023847 009970 INITIALIZE
023850 009B00 SET 023851 009B06 SET
The offset in your abend message referes to HEXLOC in the compile output. You should find the nearest HEXLOC to your offset, then the LINE in the compile output should be the offending line causing the abend (note the HEXLOC and the offset usually are not the same, so you need to look for the closest match).
Hopefully you'll be able to do this. There are other tools you can use such as Abendaid, Fault Analyser etc. but I don't know if you have these products installed. Perhaps talk to your local friendly Systems programmer who should be able to help.