Assalamualaikum, as the question says, how many Sunnat rakats do I need to perform before or after Jumma prayer(friday).
You need to separate what's considered Friday prayer with what's considered something else.
Friday prayer is kutba + 2 rakat
Now there are sunnah prayers associated with the Friday prayer and those are the same as dhuhur.
Before the prayer = 2 or 4 rakat (depends which school you follow, for shafi'is the sunnah is fulfilled by doing 2, for hanafis the sunnah is fulfilled by doing 4)4)
After the prayer = 2 rakat
So these are all the prayers that are associated with the Friday prayer.
Additionally, there's a sunnah prayer called "salutation of the mosque", which are the 2 rakat you perform when you enter a mosque. Since people go to the mosque for Friday prayers, they usually do this sunnah as well.