star - How to interpret extreme ultraviolet/ x-ray data in the literature?

The EUVE catalog gives you a count-rate in a certain EUV band. To convert this into a flux, you need a flux conversion factor to go from counts per second to energy flux at the Earth per second. This conversion factor, also often known as an "ECF", depends on the intrinsic spectrum of the source and also how much absorption (known as the hydrogen column density) there is between Earth and the source. So there is no one answer that can be given.
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Your best port of call is the PIMMS flux conversion tool, which has an EUVE module and can do these flux conversions for you if you know something about the spectrum and the absorption. I'd try it for you but I couldn't immediately see how to do it for EUVE, though it claims the information is there...

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