You have to upload all your input RAR files to this website and it will convert them all to ISO format. Besides ISO, it also lets you convert RAR to other formats such as 7Z, CAB, ZIP, TAR, JAR, etc.

Once installed, open File Explorer, select and right-click on the folder you want to convert, then choose Build an ISO Image. On Windows 11, click Show more options in the context menu to view ...