How would you deal with these missing values??? (under time crunch)

I have a large data set (12,388,912 by 84). Say each row represents an individual customer, with location info (state, and county) and an important associated dollar amount. For part of my project, I need to know, for one specific state, how many customers there are below a certain dollar amount threshold for each location (. It is important that this number is as accurate as possible as it will be used in some other calculations later.

The problem is …

county customer customers data datascience data set deal location missing values part project set state values