I’ve linked to sources for magnetic declination, the difference between true north and magnetic north, in the past. But for the current value, the Magnetic Declination website may be the easiest to use. When you visit it, it will determine your location based on your IP address, and give you a Google Map view with pop-up showing magnetic field data for your position, including the declination. But you can also scroll the map to any location, click on it, and get comparable data for that spot:
To correct a magnetic compass bearing to a true bearing, add the magnetic declination if it’s described as POSITIVE (as above), subtract it if it’s negative. I do wish it gave values in decimal degrees, but it’s not too hard to convert DM to decimal (divide minutes by 60, add to the degrees).
Inclination is the angle of the magnetic field relative to the surface at that point; good compasses often have the needle weight balanced to compensate for the magnetic field angle, which otherwise would cause the needle to skew forward or back. Since the angle shifts from positive to negative as you go south across the “magnetic equator”, this needle balancing is usually optimized for either the Northern or Southern Hemisphere for a particular compass. More expensive compasses are available with balancing systems that will work across most of the globe.