Just wanted to ask if I am allowed to use these for commercial purposes after I have paid for them?
"licensed under CC BY 4.0 
".
"You must give appropriate credit , provide a link to the license, and indicate if changes were made . You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use."
If you're willing to sell any video-games or digital content in which contains this base pack, you would need appropriate credits (artist, link, etc.) and you're not allowed to claim it as your own.
But yes, you can.