PacletFindRemote
PacletFindRemote["name"] gives a list of paclets that match "name" available on known paclet sites.
PacletFindRemote["name"->"version"] gives a list of paclets that match "name" and "version" available on known paclet sites.
PacletFindRemote["name",<|prop1->val1,prop2->val2,…|>] gives a list of paclets that match "name" and criteria given by the propi->vali available on known paclet sites.
Please visit the official Wolfram Language Reference for more details and examples on core symbols.