The first functional instruction is the opcode and the second is the operand. The later of the two operands is the source operand and the earlier is the destination operand. You should know this if you have studied microcontroller.
Machine code can be found in the textbook,
1, 74H
10H
2, 90H
20H
20H
3, F0H
It is not necessary to think about the machine code at this point, what was your original intention?