That is, how to use:
known wire length, diameter/area, resistivity
to calculate the required volts/amps to heat the wire to 30 degrees Celsius?
Can't be done without a good deal more information.
To start, you must specify the thermal value of the wire insulation. Second, you must specify the surrounding environment - what is it's temperature, what material surrounds the wire, and what is the velocity of the surrounding material.
You also need to specify exactly how the wire is configured.
So, what is the surrounding medium? Air? Water? Oil?
How fast is it flowing?
What is its temperature? Just as an illustration, if the wire is suspended in air at 30 C, it will require 0 volts and amps for the wire to reach 30 C. Or are you asking for a 30 C temperature rise above ambient?
Is the wire insulated? If it is, it will heat up more for a given power.
Configuration - Is the wire suspended in more-or-less a straight line, or is it formed into a tight coil? If it is a coil, heat lost from any part of the wire will tend to heat another part.
Unless you can provide all of these details, your question is unanswerable.