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. This is often easier than the Instagram app as it is a bit more clear.
To check, go to the Facebook Page that you want to review. For a list of all Facebook Pages that you manage, head to this link. That link displays both Facebook Pages you own via Business Manager and those that you have been shared access to outside Business Manager (such as a client sharing access).
Then click the Facebook Page you want to check.
From the Facebook Page, click Settings in the top right corner:
Then in the Facebook Page Settings section, you will see "Instagram" on the left hand side:
On that settings page, you will see the Instagram Business Account associated with the Facebook 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 bottom of the Instagram settings page.
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.