Originally Posted by OurWorkbench

Welcome to Quilting Board.

Yes, that machine uses the commonly available sewing machine needles. The 100 is the metric measurement of the shank. That is a larger needle for heavier material. There is a lot of information on the web about needles and the corresponding thread and fabric to be used. Here is a link to a chart that a lot of Singer manuals had http://web.archive.org/web/201102250...g_needles.html Some other links that may be helpful.
https://web.archive.org/web/20130910...didyouknow.htm
https://www.flickr.com/photos/toriejayne/24045388550/
https://www.ageberry.com/sewing-machine-needles-types/
https://www.ageberry.com/sewing-mach...zes-explained/
There are a couple of threads on another forum that have some good information one is called "Thread size, needle size, and stitches per inch in ye Olde Days" and another is "Does anyone understand Coats & Clark thread designations?"

There is a sticky thread here How to Clean Up and use a vintage sewing machine - videos by Muv and Fav

There is a manual available for your machine at https://www.manualslib.com/manual/10...inger-Vs1.html

Congratulations on getting a treadle sewing machine and have fun.