Compound interest calculation

Heya,

I would like to understand the formula behind the following issue:
I am contributing each month to a pension fund some money, I would like to calculate the yearly % on investment.
=RATE is used for loans, but by using the =FV and plugging my own numbers periods/starting money/end capital etc, I can change the rate until I manually hit the sweet spot, but how can I put it into a formula.

Lets say:
Starting capital - 278.96
Period (Years) - 7
Yearly contribution - 300
End capital after 7 years - 2883.31

So by using =fv and manually changing the rate it is supposed to be 5.47509% growth YoY, but how do I get it with a normal formula?
I hope my question is understood, it's possible that I am not looking for the right keywords as I am not native EN.