icloud shows backup thats not there, how to reset /delete/format icloud space??

my icloud shows 2.9 gb used... and on iphone or ipad i am not able to see whats that 2.9 gb so that i can delete..

but in icloud control panel on windows on managing, i see backup of 2.9 gb but nothing is there and cant be deleted..

please help me how to increase the space..

i havent used the icloud in a long time and last time i used it was on a different phone, that i dont have.

also, maybe the backups that i did might not be fulfilled fully thus leaving a space discrepancy..

how to sort it, please help