How do I know if there were any installment sales reported on box 17, Code K of my K-1? It just says "K1_179"

I am assuming your K-1 form is from an 1120-S tax return. 

Box 17, code K is for dispositions of property with section 179 deductions, so K1_179 just refers to that.

If this amount is from an installment sale you should have an attached statement that says so. Check to see if there is a K-1 statement that has additional information for box 17, code K. If there is no such statement, you can assume it was a regular sale.