how do i get windows 7 home premium installation file?

My son who has a Dell Inspiron One 2320 with Windows 7 Home 64bit.

Having just spent many days working with help of some guys on a form, we managed to recover the PC back to working where it would start etc.

My son has not got a image of Win7 as it is a Dell OEM installation as found out by entering the product key to Microsoft.

Can a image be downloaded in the event of needing it to repair the PC and many files were corrupted everywhere.

If so, from where. Tried several of the old links found here and are dead.

Otherwise as I have a Windows 10 iso and media creation tool, could upgrade his Win7 to Win10