Let me inform you, when you download files using RealPlayer the downloaded Music / Videos will be saved in your hard drive. RealPlayer will only have a shortcut to that file in RealPlayer library. It wont store the Music / videos in any external server.
If you have the back up for those files in your computer hard drive or with any external storage.
Once you install the RealPlayer latest version from www.real.com You can do a scan disk for media to import the files from your computer hard drive to the RealPlayer PC library.
To do so, follow the steps in the below article:
https://customer.real.com/hc/en-us/articles/205035417
Note: If you don't have the back up for those files, then you have to download once again from the source you downloaded before.