[{"_id":{"$oid":"61e3f899d0d1470401cebe13"},"name":"Item A","price":"5"},{"_id":{"$oid":"61e3f8a2d0d1470401cebe15"},"name":"Item B","price":"10"},{"_id":{"$oid":"61e3f8c2d0d1470401cebe17"},"name":"Item C","price":"20"},{"_id":{"$oid":"61e3f8cfd0d1470401cebe19"},"name":"Item D","price":"9"}]

db.collection.find({$expr:{$lte:[{$toInt:"$price"},9]}})