I would like to give my players some spells from Hellfrost - but Hellfrost uses a penalty to the casting roll instead of Power Points cost. How can I convert those spells for use with Power Points?
The penalty to casting roll is now an official variant rule in Savage Worlds Deluxe. It's detailed in the Setting Rules section on page 85. I don't have access to Hellfrost, but being Savage Worlds the math is going to work out the same, so we can use the core system's variant rules to convert Hellfrost spells to Power Points rules.
In short, Power Points and roll penalties trade on a 2:1 basis, so a 4 PP Power would instead impose a -2 on the casting roll, and vice versa. Therefore, simply double the absolute value of the Hellfrost spell's penalty to find the PP that is appropriate for that Power.
Going from PP to penalty we're told to round down, so 3 PP cost would become a -1 penalty. Therefore, feel free to bump a Hellfrost spell's converted PP up a point if it seems like it's slightly more powerful, or even just to get some variation in the costs instead of having them all be a nice even multiple of 2.