Presumably you have a candidate who no longer qualifies for licence conversion as the NPPL was issued after 8th April 2018. If it was before that date, then he qualifies as per CAP 804 Part 4 Section P.
To meet the requirements for initail issue of a LAPL that does not fulfill the conversion criteria, then the following minimum training is required:
15 hours dual training
6 hours supervised solo inc the solo cross country
You can credit the rest, except that the credit must not exceed the total PIC time that he has accrued.