You can’t convert one to the other
You can’t convert a vantage score to FICO. They use different scale, different formulas, different weights and emphasis on the items from your credit report etc.
Roughly, you can expect your FICO to be ~100 less than your vantage, but that is only because Vantage ranges from 501 to 990 while FICO ranges from 300 – 850.
Click here for a visual comparison between Vantage and Fico scores.
You can’t do much with your vantage score. The 3 major credit bureaus try to sell them to consumers, but ~90% of creditors use the FICO, so…
Don’t waste your money on buying Vantage score. They’re useless. If you want to get a sense of what your FICO is – go to CreditKarma. They give you a free score based on you Transunion credit report. It is also not an actual FICO, but according to numerous users – it’s very correlated and within less than 50 points from your FICO.