You already know how to count in 10s.
10 20 30 40 50 60 70 80 90 100
Your answers are actually the 10 times table.
Here is the 10 times table.
Try to learn it by heart.
0 × 10 = 0
1 × 10 = 10
2 × 10 = 20
3 × 10 = 30
4 × 10 = 40
5 × 10 = 50
6 × 10 = 60
7 × 10 = 70
8 × 10 = 80
9 × 10 = 90
10 × 10 = 100