LDA #3       ;desired row
ASL A        ;Times 2 bytes per row (if the array's row size wasn't a multiple of 2 we'd need to actually do multiplication)
             ;which the 6502 doesn't have in hardware but can be simulated by repeated adding.
CLC
ADC #1       ;desired column (since it's 1 byte per column, we can skip the part where we multiply desired column by bytes per column)
TAX          ;move A to X so we can use it as the index

LDA Array,x  ;evaluates to LDA #40