Depends on the client, but drop the NOSTR: part off and search just the nevent. I prefer nostr.band for search.

nostr:nevent1qqsfgunwjy4etu3m7sm2wa7v3qlkkn54y75m6uwfdysecrz05qyuq9cpz9mhxue69uhkummnw3ezuamfdejj7q3q9dthxrkpe3rd94t97p9a4svnqqmr8kvznm8eyqy70yrxh884c0kqxpqqqqqqzhx52hs