Welcome to the forum!

In the Montage manual we have this sound list 1-2036 sounds.

How to convert all this sounds to 1-127 program change messages?

You will need to send the MSB, LSB and PC number of the performance.

This FAQ tells you how to find the MSB, LSB and PC number for the current performance. The PC value shown is 1-based so you need to subtract 1 from it.

https://faq.yamaha.com/usa/s/article/U0009187

Do you want to load an entire performance? Or just one part?

There are different LSB values that can be used if you just want to load the first part of a performance. See the data list p.127

https://usa.yamaha.com/files/download/other_assets/5/812525/montage_en_dl_c0.pdf

The first set of 'Bank Select' items in the table are 'Performance (Single Part) - Can be used when only specified Part is changed'

Using those LSB values lets you REPLACE a part (e.g. part 3) with the 1st part of the performance you reference.

On the set at the right the LSBs are labeled 'Performance (Multi Part) - Can be used when all Parts are changed'.

We suggest you load the Multi/GM performance which has 16 parts and then try different PC commands to replace either certain slots or the entire performance.

When replacing a single part you need to send the PC command on the channel that part is receiving on.