The file you must edit is called cmndr.0 which you will find in
your Tank Commander (e.g. TANKGAME) directory.

Here we have an example with only one commander called RAIDER

00000000 52 41 49 44 45 52 00 00 00 00 00 00 00 00 00 00
RAIDER..........
00000010 00 00 00 00 31 47 32 41 33 41 35 41 36 41 37 41
....1G2A3A5A6A7A
00000020 38 41 2A 41 2A 41 00 02 00 04 00 06 00 09 00
8A*A*A.....

The line with 1G2A3A5A6A7A and 8A in the next line represent the
missions. Now grab the hex editor and change your missions like
following:

Mission 1 - From 1A To 1G
Mission 2 - From 2A To 2H
Mission 3 - From 3A To 3E
Mission 4 - Doesn't exist
Mission 5 - From 5A To 5F
Mission 6 - From 6A To 6E
Mission 7 - From 7A To 7F
Mission 8 - From 8A To 8E
Mission 9 - Doesn't exist