The maximum size of fan your case supports is 120mm.
specs: http://www.coolermaster.com/case/mid-tower/k350-rc-k350-kwn2-en/
If you only have one 120mm at front and want to populate all fans slots then you'll need 3x 120mm fans.
For good and quiet case fans, i suggest Arctic F12 PWM.
specs:
https://www.arctic.ac/eu_en/arctic-f12-pwm.html
pcpp:
http://pcpartpicker.com/product/cXg323/arctic-cooling-case-fan-afaco120p2gba01
Or if you want some eyecandy via LED fans (red, blue, white), then go for Cooler Master JetFlo fans,
specs: http://www.coolermaster.com/cooling/case-fan/jetflo-120/
pcpp: http://pcpartpicker.com/products/compare/Gx4gXL,NvphP6,L4rG3C,MwR48d/