use Kociemba
A cube definition string "UBL..." means that in position U1 we have the U-color, in position U2 we have the B-color, in position U3 we have the L color etc.
according to the order :
U1, U2, U3, U4, U5, U6, U7, U8, U9, R1, R2, R3, R4, R5, R6, R7, R8, R9, F1, F2, F3, F4, F5, F6, F7, F8, F9, D1, D2, D3, D4, D5, D6, D7, D8, D9, L1, L2, L3, L4, L5, L6, L7, L8, L9, B1, B2, B3, B4, B5, B6, B7, B8, B9.
So, for example, a definition of a solved cube would be
UUUUUUUUURRRRRRRRRFFFFFFFFFDDDDDDDDDLLLLLLLLLBBBBBBBBB
Solution string consists of space-separated parts, each of them represents a single move:
A single letter by itself means to turn that face clockwise 90 degrees. A letter followed by an apostrophe means to turn that face counterclockwise 90 degrees. A letter with the number 2 after it means to turn that face 180 degrees. e.g. R U R’ U R U2 R’ U