Your individual NPI is used to report MIPS.
The 24J field on your claims should contain the individual NPI. The TIN in field 25 and the individual NPI listed in 24J should always be used to report MIPS.
If you look at your claim forms you will see that there are two different spots for NPIs. The 33a field is where the Group NPI is listed. Please do not report MIPS using the Group NPI.