Formula Help - search/compare values in data array

I have the following Data schema set up (for an airtable api):

I created a collection Data variable (data.airtable_students) that gets the records array. I need to be able to check the value of “Key” (in the ‘fields’ object).

I tried doing: IS_IN_ARRAY(data.airtable_students, “12345678”)

but that didnt work. You can see in the records below it is there.

{
“records”: [
{
“id”: “recZ3vOvT5L5Ip83W”,
“fields”: {
“Key”: “12345678”,
“Name”: “John Doe”
},
“createdTime”: “2020-07-06T12:20:19.000Z”
},
]
}

So the example above, how do i make a formula that just returns true or false if it finds “12345678” in any returned records?

Nevermind I figured it out.

FIND(data.airtable_students, item.fields.Key == “12345678” )

Thanks anyway

But how do i get the index of that record so i can copy or assign that record to another variable?

You can try INDEX_OF