How do I see a breakdown of refund.i don't think I received my whole refund for 2020

Then look at line 35a of your 2020 Form 1040 and somewhere near the bottom of whatever state return you filed.   Do some math and compare that with the amount of refund you actually received.   If the IRS or state reduced your refund they send you a letter explaining why the refund was reduced.

 

Or look at your federal transcript:

 

You can get a free transcript from the IRS:   

 

https://www.irs.gov/individuals/get-transcript

If you believe you did not receive your full refund amount, please click here for some information regarding why your refund may be less than expected.