Update Premium WordPress Theme

Hello Guys;
i am little-bit confused. Actually i want to upgrade my free theme to premium wordpress theme. so if i do then what will happen with my plug-in files?
actually now i have around 1k post and i am using all-in-one seo pack, so my confusion is that my installed plug-in(all-in-one seo pack) and also files will be remove or not..?
please help me it’s urgent

thank you….