Converting current to constant USD values for trade data (UN Comtrade) I am using WB (country GDP) data in combination with UN Comtrade (bilateral trade) data. I need to divide bilateral trade by GDP so as to find out which % of a country's GDP comes from bilateral trade. 
The problem is WB has values in constant 2010 USD while UN Comtrade in current USD. 

How can I transform the current USD values in constant 2010 USD values?
Use the World Bank data on US inflation to deflate the UN Comtrade dataset, so that it is also in constant prices.

Select Download, at the right side of the page, and you can get the dataset in csv or other formats.

To deflate the trade data, simply divide the values of bilateral trade by the value of each years CPI index, and then multiply them by the value of CPI in 2010 (the base year, which is 100 in this case). Alternatively, rebase the CPI index, by dividing all values by 100, so that CPI in 2010 is equal to 1. Then, divide the trade data by this new index. Both approaches are equivalent.