Valid JAR-FCL PPL (A)
Valid JAA Class 2 medical
Expired SEP (2 months ago)
Your JAR-FCL Licence
IS an EASA Part FCL Licence, so you don't need to 'convert' it until it needs re-issuing at the end of it's 5 year validity.
Your SEP Class rating needs to be 'Renewed' as it has run out.
To do this under EASA, go to an ATO/RTF (Flying School) and ask the Head of Training (HoT) there for an assesment of the training you may need before attempting the 'Renewal' Proficiency Check (PC).
If you are in current flying practice, and your SEP Class rating has only run out for two months, He
may asses that you do not need any training, but in any case he needs to sign a 'Course Completion Certificate' (CCC) to confirm that you have completed any required traing, before you can take the PC.
Then take the CCC to an Examiner and complete the PC. As it is less than 3 years since your SEP expired, the Examiner will sign your Rating Page, and you are done.
If you are also approaching the end of the 5 year validity of your JAR-FCL Licence, you will then need to apply for the re-issue as you would have in the normal course of events, and it will be re-issued as a 'valid for life' EASA Part FCL Licence.
Don't worry about the forms you need.

The HoT and Examiner will print these off for you, and help you fill them in.
MJ