How to reduce file size?

[mediamonster]

My WP site has 7 pages total and about 12-14 images. Max image size is 300kb
But the file size is over 350MB.
When I tried to transfer the site to another host using a plugin, it says the file size is huge so it can't transfer unless I buy upgrade.

Now I'm wondering what made it so big in size!

Your suggestion will be highly appreciated.

Sorry, I didn't understand your query here. What do you mean by 'file size' here? Is your database size 350mb long?