It really depends. If Vegeto truly is multiplying the two power levels together, at Vegeto's weakest he would be 9 Trillion. If you just count base Gokou's level in Freeza's saga. Then from that Vegeto would be 100x more powerful since he could go ssj2l. And Gokou's and Vegeta's base level is way higher than 3 million.
And by those figures also, and added to GT level. Base Vegeto is just slightly weaker than SSJ4 Gokou.
Base Goku fused with base Vegeta to make base Vegeto. If the battle power(*)battle power concept from the Daizenshuu holds true for a perfect/ideal Potara fusion(of which Goku and Vegeta were certainly touted as), then Vegeto's [theoretical] base PL would be closer to 8 quadrillion(15 zeroes after the 8), assuming Goku and Vegeta's base PLs were each around 90m at the time.
You would then multiply that figure by 100x in order to figure out SSJ2 Vegeto's [theoretical] PL; which equates to roughly 800 quadrillion.
Most people will never accept such a notion, because frankly, that is an utterly absurd figure... But at least it's not a baseless utterly absurd figure. 😉