Find and update content type on a item

_api/lists/getByTitle(‘Site Pages’)?$expand=ContentTypes&$select=ContentTypes/Name,ContentTypes/StringId

{
“content-type”: “application/json;odata-verbose”
}

first(body(‘Filter_array’))?[‘stringid’]

_api/web/lists/getbytitle(‘Site Pages’)/items(1)

{
“content-type”: “application/json;odata=verbose”,
“if-match”: “*”
}

{
“__metadata”: {“type”: “SP.Data.SitePagesItem”},
“ContentTypeId”:”@{outputs(‘Compose’)}”
}