Man pages matching name pmdainstance in section 3:

pmdaInstance.3.en	debian 10 / libpcp-pmda3-dev
pmdainstance.3.en	debian 10 / libpcp-pmda3-dev
pmdaInstance.3.en	debian 11 / libpcp-pmda3-dev
pmdaInstance.3.en	debian 12 / libpcp-pmda3-dev