Sorry, my message might have not been clear enough.
In fact, if you have 1-99 pictures belonging to the same archive / having the same provenance, you should batch rename with a software that forces the file name to end with two numbers: 01, 02, 03, ...09, 10 (and so on: 1-999 pictures, 001, 002, 003, ...099, 100, ...).
Like this, if the first part of your file name remains unchanged, Tropy (which is considering the pictures name as an alphanumeric string) will sort your files from "N96 6 fevrier 1751 -01" to "N96 6 fevrier 1751 -13".
Among, I suppose, many other programs, Xnview provides a batch naming tool. To rename your files, forcing it to double numbering, you should use this string in the tool:
- N96 6 fevrier 1751 -##
[by using N96 6 fevrier 1751 -# instead, you would obtain the same naming you actually have]
In case you have also documents from February 1751, you should use this string:
- N96 06 fevrier 1751 -##
Documents from the same month would be grouped together, but (e.g.) documents written in Avril would come first
Or, even better:
- N96 1751-02-06 -##
Documents will be sorting (during import) according to their call number and then their date
If you have already inserted photos in Tropy, consider grouping them in Items, where you can change their order easily.