I have a 13” 2019 Macbook Pro and an LG 27GN850 monitor. What adapters do I need to use together?

1. Be careful with that built-in display on your Mac, because it's much more vital than the ones on other Macs. I had the exact same Mac and the display broke as shown below:
2. It depends on the port selection on the monitor, I tried looking it up but I still couldn't find a image that let me see the io very easily. If it has an HDMI port, USB-C to HDMI, VGA, USB-C to VGA.

that display also has a DisplayPort input, and specs say it is ready to give better results over DisplayPort:

• DisplayPortYes (1ea)DP Version1.4
• DP (Max. Resolution at Hz)2560 x 1440 10bit at 144Hz [(only 8-bit over HDMI)]

an adapter like this would give good results for DisplayPort. But there are many others.

Monoprice Select Series USB-C to Mini DisplayPort Adapter - Product # 24273- $14.24  

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you can use an adapter like the Tripp Lite USB C to HDMI Video Adapter, and an HDMI cable of sufficient length. and if the HDMI cable needs to be more than about 10 FT in length, I recommend you shop for an active HDMI cable, such as the Monoprice High Speed HDMI Cable - 30 Feet.

to go HDMI, you want the USB-C Digital AV Multiport Adaptor Model MUF82AM/A