changing http – https on multiple images

Am considering adding ssl to my site. – theroyalpen.com

I keep hearing and reading that we do not need to add ssl when using PayPal..but am thinking I should have it because people fill out the shipping info onsite before going to PayPal, and it will make shoppers feel more secure.

Question is..I have hundreds of images of products (http) that have already been loaded without ssl(https), how do change these so they don’t initiate an ssl error message when the pg is loaded?
Is there a way to do a mass correction or would they have to be corrected one by one? (If at all)

https://wordpress.org/plugins/better-wp-security/