where can i get roadworthy certificate

In Australia you get a roadworthy from an authorised inspection station, not from your cousin with a torch and opinions.

In Victoria, book a Licensed Vehicle Tester (VicRoads-approved) for an RWC; in Queensland it’s a Safety Certificate from an Approved Inspection Station; NSW uses eSafety “pink slip” checks at authorised workshops. Most are regular mechanic shops or mobile testers—find them via the state authority’s directory (VicRoads, Service NSW, TMR QLD, etc.) or a quick local search. Expect a check of tyres, brakes, lights, leaks and structure; it’s roadworthiness, not a spa day. Prices vary by state and vehicle, so ring around and book ahead. If it fails, you’ll get a fix list and a window for reinspection—thrilling stuff.