i delete unattached photos ,many of my site images are deleted.

Hi asadujjamanhira03,

Thanks for reaching to us.

It’s hard to give you exact reason caused that, in case you want to get images back so you can create a dev site and import any template there. Devsite – also called a Staging platform where you can test issues, enable/disable features/plugins thus such changes will affect the main site. The below article will help you to create it:

https://www.wpbeginner.com/wp-tutorials/how-to-create-staging-environment-for-a-wordpress-site/

Finally, go to Tools > Export > select Media then import xml file into your live site.

Kind Regards,
Hung PD