Hi @RahmaSallm
On the Prime main Dashboard, there´s a dashlet under Metrics called Unified AP Status. It shows in percentage how many APs is Disassociated in a Red Button. If you click on it, it will list all the currently Disassociated APs. Then you can export in csv format by using the icon on the top right corner.
You can also Sync the WLC by selecting the required WLC on Configuration Tab, Network Devices , Wireless Controller. Select the appropriate WLC and click Sync button on top.
-If I helped you somehow, please, rate it as useful.-