Propel likes to have the table relationships defined in the Schema file, so, begin with your schema files and create a foreign key relationship (add options depending on the type of relationship that exists in the data):
<table name='confirmation_request' ...
<column name='id' ....
...
</table>
<table name='confirmation' ...
...
<column name='cr_id' ...
<foreign-key foreignTable='confirmation_request' ...
<reference local='cr_id' foreign='id' ...
</foreign-key>
...
</table>
Then you can write queries like:
$crs = ConfirmationRequestQuery::create()
->join('ConfirmationRequest.Confirmation')
->where('Confirmation.UserId = 10') // Add other conditions as required
->where('Confirmation.DeviceId = ?', $define->getId())
->where('Confirmation.Id IS NULL')
->find();