These words are similar, but there is a slight difference. A 'springboard" has the added meaning of a step towards your goal that also has extra energy or movement to help you progress faster. トランポリンのようなものを想像してください A "stepping stone" does not move, so there is no extra energy or movement. But it is still a good thing. Good luck!

‘Springboard’ is often at the beginning and is a way to make important progress quickly. A ‘Stepping stone’ gives you forward progress, but it’s not necessarily important. Your sentence isn’t right with either word. You could say for example: I use my mistakes as a stepping stone. I learn from them.