The conversion for Kelvin from Celsius is simple since the units change at same rate (degree for degree) but haven't different zero reference. The Kelvin scale represents absolute zero. The celcius scale moves degree per degree with kelvin scale but has a zero based on freezing point of water. The conversion is 273 + (temperature in celcius) = temperature on kelvin scale. Note 273 is a rounded number to nearest whole number. The actual figure is a number with decimal. 273.15 can also be used if you want more significant figures.
so 273 + 78C = 351 K