Start FM7 in standalone mode and make sure FM7 is receiving MIDI from the DX7 or TX7 (which must be connected with the MIDI output to an input port of your midi interface). Make sure that in the FM7 memory protect is turned off (under PREF).
Now start a SysEx dump on the DX 7 / TX7. The FM7 will immediately start loading the transferred sounds. You will see that the preset names on the library page will change. Then, on the FM7 library page press the Save 32 button to save these 32 presets into one file on your hard disc or press the save all button to save all current FM7 settings including the 128 presets into one file on your hard disc.