The export price indexes presented in the International Financial Statistics (IFS) are collected from country statistical offices, then re-referenced to a common reference period of 2010=100. The IMF Export and Import Price Index Manual (https://www.imf.org/external/np/sta/xipim/pdf/xipim.pdf ) notes that export price indexes are valued from the perspective of domestic sellers.  Prices should be collected in the transacted currency, then converted to the national currency. The following excerpt from Chapter 11 paragraph 140 of the manual describes the process:

…any prices reported in foreign currencies must be converted to the national currency using an exchange rate. According to the SNA 2008 (paragraph 3.136), the data should be converted using the exchange rate prevailing on the date of the transaction, and if that is not available then an average exchange rate for the shortest period possi ble may be used for the conversion. For example, the U.S. BLS price reference period is the first of the month, so it uses the average exchange rate for the previous month. Note that there are usually at least two different exchange rates for any given date, namely, the buy rate and the sell rate. To exclude the service charge represented by the difference between these rates, the midpoint between these two rates should be used. Likewise, if the rate includes a forward exchange cover, that should be removed. The exchange rates are usually not provided by the respondents, but rather are collected each period by the statistical agency from official exchange rate publications.