According to Jain scriptures, in his immediate previous birth Bhagwan Vasupujya was:

• King Padmottar (Padmottara Raja)
• Ruler of Mangalavati Nagar
• In the Ardha‑Pushkar (Ardhapushkar) Dweep of Mahavideh Kshetra

There is no major difference in this point between Digambar and Shwetambar traditions – both accept that his last birth before becoming a Tirthankar was as Raja Padmottar.

You can read a short Jain-style summary here