Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from San Juan to Moscow as you normally would.
SJU stands for San Juan Luis Munoz Marin Intl Airport, while VKO stands for Moscow Vnukovo Airport. These codes are often called IATA codes, a set of identifiers established by IATA (International Air Transport Association) that is widely used by airlines and the aviation industry. Moscow Domodedovo Airport (DME), Moscow Sheremetyevo Airport (SVO), Moscow Zhukovsky Airport (ZIA) are some additional IATA codes for airports related to your trip.