The only way to convert .adp files from Microsoft Access to .accdd files, would be to use some of the later versions of Access that does support .accdd files. No other program can probably help you with adp to accdb conversion, as MS Access formats are proprietary and not well supported in 3rd party software.
When you have opened your .adp files in MS Access, you can simply use File ► Save as.. function to re-save your databases to ACCDB format.