50million as scientific notation = 5x10^9?

False! It is 5 × 10⁷.

50 million is 50 000 000.
50 000 000 = 5 × 10 000 000
Count number of zeros - it is your exponent:
in 100, there are 2 zeros, so: 100 = 10²
in 1000, there are 3 zeros, so: 1000 = 10³
in 10 000 000, there are 7 zerose, so 10 000 000 = 10⁷

50 000 000 = 5 × 10 000 000 = 5 × 10⁷

The graph isn’t that clear