Hi. One of the best sources I had for overall training/retraining was to join LinkedIn Learning for the free trial month offered. You should find some good training modules in there for overall Excel, and I'm fairly certain there are ones with a finance focus.
Excel: Financial Functions in Depth Online Class | LinkedIn Learning, formerly Lynda.com

That particular one is for Excel 2016 but you can search for the version of Excel/Office that you have. When I used it four years ago, several versions were supported.

Another thing you can do is check out some YouTube tutorials. A search string like https://www.youtube.com/results?sear...ncial+formulas
yields a fair amount of content.

https://www.youtube.com/results?sear...stics+tutorial
also yields some promising looking results.

Some of the channels I use for Excel tips are Leila Gharani, Kevin Stratvert, MyOnlineTrainingHub, and ExcelIsFun.

Best of luck!