It depends on your parents.
For me, I just showed my mom how much I knew about them and kept showing my mom pictures and videos of cute hedgehogs, and for my dad, I assured him that they were not rodents and made a PowerPoint presentation on hedgehogs and why I should get one. What I’d recommend is show your parents how much you know about them (pictures and videos would help) and make sure they know how much you want one. Also remind them of how well you took care of your other pets. It may take time to convince your parents to let you get a hedgehog, but once you have one, you’ll realize it was very much worth the wait.