You can also use the LongToDateTime action in the CommunityCommons module to convert a Unix timestamp to a DateTime object. There is also DateTimeToLong if you need to go the other way.
Hope this helps
Hi Shivprasad,
Your timestamp appears to be an amount of milliseconds since the epoch (jan 1, 1970).
You could convtert that to a datetime in Mendix through:
addMilliseconds(dateTimeUTC(1970,1,1), 1590658020461)
For me that seems to give the correct answer: may 28, 2020 9:27:00 (UTC)
Regards,
Jeroen