Each Instagram Business Account is associated with a single Facebook page. That means that each Instagram Business Account has a single page as the "owner".
You can't have multiple Instagram accounts "owned" by the same Facebook page – it is always 1:1.
The "owner" page is different to adding a certain page as the page you share Instagram posts to (or run ads associated with) – when you convert an Instagram account to a Business Account you'll nominate the page that owns the account.
The easiest way to check which Facebook page is associated with which Instagram account is on the Facebook website on your computer right here. This is often easier than the Instagram app as it is a bit more clear.
Click here on "Linked Accounts"
Then you will be able to see which IG account is connected to your FB page. Here is our Facebook page - associated with our Instagram account @getskedsocial:
If the Facebook Page is connected to the wrong account, you will see a 'disconnect' button at the top of the Instagram account info area.
If no Instagram account is currently associated with that Facebook Page, you will be able to connect it from there. If needed, this will also convert the Instagram account to a Business Account.
As always, reach out to our support team if you need anything!