.t64 is Commodore 64 Tape Image File
Key Features: .T64 File Extension
What is an .T64 file?
File extension t64 is mainly related to a special Commodore 64 emulator tape file format. This format was designed by Miha Peternel for use in his C64s emulator.
Files with t64 suffix are in most cases emulators tapes saved in Commodore 64 format which is accepted in most emulators.
How to open:You can use .t64 files in several Commodore 64 emulators, including WinVice and CCS64.
How to convert:A conversion of .t64 file seems unlikely.