You have the right idea. You'll apply a y-axis reflection to go from above the x axis to below it. This allows us to move the red line into the correct vertical position without having to use a vertical translation.
Afterward, you'll shift the red line 4 units to the right to have it line up perfectly with the blue line.
Going from f(x) to -f(x) is the y-axis reflection part
Going from -f(x) to -f(x-4) will shift the line 4 units to the right.
Answer: g(x) = -f(x-4)
