Three things that I can see:
if(mission.length === checks.dataEntries)mission.length is an integer, which is good. But checks.dataEnteries is the entire object, which is bad. You need to access one of the values in dataEnteries instead.
mission.lengthis actually the wrong integer, because
missionis the property key as a string, so you’re coming up with how many characters are in the string. You need to access the value of the property instead.
Your for loop and if statement seem to be structured such that if any of the tests pass, you return true and the function stops executing. You won’t return false if only one of the tests fail.