Do you mean I've to apply for partner Visa first?
How do I know that they will grant me a no farther stay visa ?If you are onshore and you are already on a visa without a no further stay condition then nothing is preventing you from applying for a partner visa now, you have no requirement for a visitor visa.
If you apply for a partner visa offshore then you can use a visitors visa to visit Australia whilst it processes but you won't be eligible for a bridging visa.
If you come to Australia on a visitor visa to see the sights or visit friends or relatives, without a no further stay condition and then subsequently decide you like it here and decide to apply for a partner visa then that would be fine, you would be granted a bridging visa.