I don't know how to do this problem!!!!!

i need to find a way to solve this problem, please help!
what is the units digit of 3^1 * 3^2 * 3^3 * 3^4 * ...........3^99 * 3^100 ?
please help me

Start out and see what happens.

3^1 = 3
3^2 = 9
3^3 = 27
3^4 = 81
3^5 = 243
3^6 = 729

Oh, let me guess, 3^7 will end in 7

3^7 = 2187

Yup.

So the pattern is 3, 9, 7, 1 and repeating.

Since that pattern has four elements, and 100 is divisible by 4, 3^100 ends in 1 (and 3^99 ends in 7).

Develop the pattern
3^1 =3
3^2 =9
3^3 =27
3^4 =81
3^5 =243
3^6 = 729

The units digits pattern is 3, 9 , 7 & 1
3^99 has the same units digit as 3^3 which is 7
& 3^100 has the same units digit as 3^4 which is 1