Hi J Chan,
You will have to work out if there is a Capital Gains liability, using UK rules for Capital Gains.
This means that you need to convert the values to GBP sterling, using a just and reasonable exchange rate in use at the time of acquistion and disposal. The disposal should be reported in a Self Assessment tax return.
Under the terms of Self Assessment, we do not provide an official exchange rate and the onus is on the individual to use a just and reasonable exchange rate for each acquisition and disposal.
For your convenience, there are exchange rates at:
https://webarchive.nationalarchives.gov.uk/ukgwa/20231016190054/
Exchange rates from HMRC in CSV and XML format and for older rates at
UK Government Web Archive/ukgwa/20100202113554/
Exchange rates from HMRC in CSV and XML format.
You are free to use any of the supplied rates or one of your own choosing.
Thank you.