How to take out filter?

I read some previous posts and found that I may need to clean the filter out at the bottom of my dishwasher. As the spray arm on the top rack is not spinning. Even though it is getting water.

After I take the spray arm off how do I take the screws out, or can I just twist the whole thing? The screws are not something I`ve seen before. Please help.

                               Thankyou, Cathy

The following should help
https://secured.whirlpool.com/Service/SrvTechAdm.nsf/2cd44500d572193285256a45004fd9d6/4e8b0d2df77cd7e585256cd800643b6d/$FILE/KD01.pdf

The screws/bolts are Torx type so you will need a set of them to remove the screws.
You should be able to pick up a set with half a dozen Torx sizes and a handle at any car parts supply or hardware store. I have a small set that cost me about $10.00.
They are very common now on cars, appliances etc.

Try to get a set that are hollow in the center.
Some devices now use a security Torx bolt. The Torx indent has a pin in the center so a standard Torx will not fit into the bolt head. This type is very common on computers.

Here is some more info on them.
Torx - Wikipedia, the free encyclopedia

Thanks for the help. I purchased the torx heads and got it cleaned out and it`s working like new!!! Thanks again for the help.
Cathy