I clean my own carpets.
I used to rent the large industrial Rug Doctor brand units.
They had a large resevoir, powerful suction and an agitating brush
I guess they were too bulky for most people - so they changed them to
a smaller (in my opinion inferior) unit.
So I bought one of the discontinued models. I share it with my family
Based on the colour of the removed water and the way the carpets look,
steam cleaning is the way to go.
I imagine referrences from your trusted friends and neighbors will
help direct you to a reputable contractor - if required.