After removing the bottom wash rack&arms how do you remove the small center bolt

Dishwasher Repair
1

after removing the lower dish rack and wash arms, how do you remove the center bolt on what i believe is the filter screen? piece of broken glass hing in screen and i believe a smaller piece of glass may have got through. washer making hi pitched noise while trying to drain

2

Here are your parts
Replacement parts for WHIRLPOOL DU941PWKQ1 | AppliancePartsPros.com

Here is a manual, although it does not specifically list your unit I believe the pump is the same as yours.
https://secured.whirlpool.com/Service/SrvTechAdm.nsf/2cd44500d572193285256a45004fd9d6/56e33eb0e839a7fa85256a8e00510938/$FILE/4322430.pdf