Tested in Build PGSQL (14300) or MSSQL (14306)
In order to find the account id, under Reports Tab, click New Query Report run the below query:
select adef.org_id "Account ID",adef.org_name "account",sdef.siteid "Siteid",sdo.name "Site" from sitedefinition sdef left join accountsitemapping asm on asm.siteid=sdef.siteid left join accountdefinition adef on adef.org_id=asm.accountid left join sdorganization sdo on sdo.org_id=sdef.siteid order by 2
or
select org_id, org_name from accountdefinition where org_name like '%sample%'
Note: Replace the sample with the account name.