Database
[{"_id":ObjectId("62aeb8301ed12a14a8873df1"),"Fields":[{"FieldId":"name","Value":["test_123"]},{"FieldId":"mobile","Value":["123"]},{"FieldId":"amount","Value":["300"]},{"FieldId":"discount","Value":null}]}]
Query
db.collection.aggregate([{$match:{$expr:{$ne:[{$filter:{input:"$Fields",cond:{$and:[{$eq:["$$this.FieldId","amount"]},{$gte:[{$toDouble:{$first:"$$this.Value"}},0]}]}}},[]]}}}])