Our Search API doesn’t support accounts, so you won’t be able to use search to do this. However, you can use the V3 Accounts API to get the list of uncorrelated accounts for a given source.
GET https://{tenant}.api.identitynow.com/v3/accounts?filters=sourceId eq "2c9180887671ff8c01767b4671fb7d5e" and uncorrelated eq true
FYI, I highly recommend you signup for developer days. On day 1 I will be demonstrating advanced reporting techniques using our APIs, including ways to convert JSON responses into a CSV format. You might find it interesting for this and future reporting needs.