MULT - MIPS instruction reference

multMultiply signed 
Multiplies $t1 by $t2 as signed 32-bit integers and leaves the 64-bit product in HI and LO.
Used in Arithmetic, logic and bitsMIPS assembly
Multiply and divide with hi and loMIPS assembly
 
Forms  mult ,   
Operands $t1 Any general-purpose register, $0 to $31, using its numeric or named spelling, such as $8 or $t0 ($zero is $0; $ra is $31). 
$t2 A general-purpose register. It may be the same register as $t1. 
The 64-bit product is split: the upper 32 bits go into the HI register and the lower 32 bits go into the LO register. Use 'mfhi' to read HI and 'mflo' to read LO.
 # Multiply 6 by 7. Inspect HI:LO: 42 (HI=0, LO=42).
li $t0, 6
li $t1, 7
mult $t0, $t1
mflo $t2
mfhi $t3