Look at the sticker on the back of your TV. It will look like OLED55B7P or 65UJ7700 .
The direct answer depends heavily on your TV's manufacturing year. Historically, LG did offer major version upgrades (e.g., jumping from 3.x to 4.x) for older models. Instead, they provided "point" updates (3.9.1 to 3.9.2) to fix bugs and maintain security. www.lgwebos.comhttps://www.lgwebos.com 4.0 update for 2016-17 Smart TV - LG webOS update webos 3.9 to 4.0