Borrow a dongle;  turn off computer;  plug in dongle; take battery out of mouse; turn on computer; ........ put battery in mouse, place it near dongle.

Mouse should find dongle, make friend with it, work as intended.

If works, (it did for me) purchase a handful of dongles on ebay.

Welcome to the Dell Community  @Vabesh 

The only reason to have a "Dongle" is if your laptop does not have bluetooth.

If your laptop does not have bluetooth then you will need to purchase/borrow a dongle.

https://www.ebay.com/sch/i.html?_from=R40&_nkw=wireless+keyboard+dongle&_sacat=0&_sop=15&LH_ItemCondition=3&rt=nc&LH_PrefLoc=1

Computers that have bluetooth should be able to link/pair to most keyboards, mice, headsets, speakers etc

Best regards,

U2

I tried but no visible devices on bluetooth, please help

NEW

Yes and hence I cannot connect them to my PC

Hi,
My laptop does have a Bluetooth, but I am unable to use Bluetooth keyboard and a mouse at the same time I have to turn off one to sue the other. And in some rare cases I am able to connect both of them. But If I shut down myu laptop or put it to sleep mode then again same issue. Anyone who faced the same issue and found any solution. I have lost my Dongle as well - Model dell ms5320wt