First thing to understand is that there exists vectors calculus and multivariable calculus, both are related but not the same. The vector calculus is what you use in EM, in griffith for the first pages or so, he explains the basic vector calculus stuff but without really detailing the mathematics. If you just want physics, then just do griffith cover to cover.
There is another book for E&M by purcell, which is 'simpler' mathematically i.e: not requiring you to 'really' understand most of vector calculus results to approach E&M. However, this book's difficulty is that in the magnetism chapter, it uses concepts of relativity to bring in the connection between electricity and magnetism... which was sort of difficult for me to understand (And...also where I stopped reading this book )
It's not something too bad, because some of the techniques used in the book have no rigorous explanation like the method of separation of variable for solving partial differential equation.
In my profile bio, I've linked an animated video textbook which covers both multivariable and vector calculus. It is where I learned it, and I think it suffices for most part, but in that course too, a good knowledge of the basics is assumed. There is also a good YouTube channel called mu prime math which has playlists of short videos where you can understand the MV concepts.
It has it's pitfalls in that it doesn't give you problems to solve, but I guess you could search up individually search up problems to do or study some questions of integration on multiple integrations in MSE(There are many many solved examples on this site, you just have to look)
A great book is the one by Strang here, it has very nice pictures to aid in understanding the multivariable concepts.