This is not an easy task. Although the technology is the same, you are entering an entirely different market place where supply and demand are unknown to you. Also, the entire scale could vary (smallest and largest charges) so applying a simple % will not be enough.
The only real way to do this is to research the market place. For instance you could compare salaries for similar roles between the two markets, and deduce an implied % change from the % change in salaries.
You could contact several companies for fictitious quotes for work, and see what you get quoted, although be careful doing this as it is not really a completely honest activity.
You could locate someone offering similar services and approach them for market insights. Most people are helpful and would have a discussion with you about it if they understood you were not an immediate competitor. Perhaps you could offer something in return but you do not have to. You could use the same approach to a potential customer too.
I would suggest checking salaries of comparable jobs would give a good insight, but there is the added complication of how freelancers are regarded in your new market place. Are they expected to be cheap, are they held in high regard, are they seen as stop gaps?
Finally, you can do what most freelancers do when starting out. Get your prices as low as possible and get a customer. Then start adjusting your prices up as you get to know the new market place and you start to build a new track record in that new location.