My website got hacked.

Hello

My website got hacked two days ago so i contacted my hosting service provider and they told me to delete whole of my website and start again. They also emailed me a backup of my wordpress database (are my posts stores in this or are they all gone). Luckily my cpanel & ftp password was not hacked so i took a backup of my themes & plugins also. Now i have again installed wordpress and i want to know should i upload my previous themes and plugins which i downloaded after my website was hacked. Are they infected and is there any way to check whether my themes, plugins and database is infected by hackers. I don’t want to get my site hacked again. Please tell me how to prevent these in future and should i upload all my data again??

Regards
Vaibhav Bathla