The Cubase song formats (.all and .arr files) are used by Cubase Atari versions up to Cubase VST 5 have been replaced by the current project file format .cprR with the introduction of Cubase SX 1, Cubase SL 1 and Cubase SE 1 in 2001. Cubase SE 3, Cubase SL 3 and Cubase SX 3 are the last versions that are capable of importing the classic Cubase song formats. Therefore, they can be used as format converter.
If you have a compatible license, you can use one of the Cubase versions available here to convert your ALL or ARR files into the CPR format, unfortunately, we couldn't verify whenever the opposite, i.e. cpr to arr conversion is possible.