External display problem

I have an LG Ultra HD display 4K. After installing High Sierra when I lookin About my mac and click display it says the display is only 1920 x 1080. When I go to system pref I can change the setting to 3860 x 2140 it will change but the fonts are to small to read for me. When using Sierra I was able to change the text size in system pref but this is no long available. Is there anything I can do for this problem?