Hi don187,
Welcome to the Sony Community!
PMB or PMH (PlayMemories Home) only manages the files stored in your computer. These software helps you import and edit the files and save them on your local drive. The default folder for all imported files transferred using PMB/PMH is the Pictures folder, unless you decided to save them elsewhere.
If by lost you mean the software has been uninstalled, simply download PlayMemories Home to manage the files using it. All the pictures and videos saved in your computer will show up on the program. But if your computer was reformatted or you're now using a different computer, you can transfer the files to the computer via USB connection or inserting the card in the slot, if they're still saved in the card you're using with the camera.
If my post answers your question, please mark it as "Accept as Solution". Thanks_Mitch