(how do I go about solving this, i know i need to conver 88days to secs and that would be 126,720. but I don't where to go from there, help please)
What is the average linear speed of Mercury about the Sun? (The distance from the Sun to Mercury is 5.80 1010 meters. The orbital period around the Sun is 88 days.)
The speed of Mercury in orbit is
V = 2 pi R/(period). Your conversion of the period to seconds is incorrect. You have apparently converted it to minutes.
Use R = 5.80 10^10 meters as the distance of Mercury from the sun.