There are a few things you can do to make sure that your UI looks the same on all monitors and resolutions in Unity:
Use the Canvas Scaler component. The Canvas Scaler component can be used to scale your UI canvas to fit any screen size and resolution. To use the Canvas Scaler component, simply add it to the root GameObject of your UI canvas. Then, set the Canvas Scaler's UI Scale Mode to Scale With Screen Size
Use anchors. Anchors can be used to position UI elements relative to the edges of the screen or other UI elements. This means that your UI elements will always be positioned in the same place on the screen, regardless of the screen size or resolution. To use anchors, simply click on the anchor icon in the Inspector window for the UI element you want to anchor. Then, drag the anchor lines to the edges of the screen or other UI elements.
Use font size multipliers. Font size multipliers can be used to scale the size of your UI fonts based on the screen size and resolution. To use font size multipliers, simply open the Font Settings window (Edit > Project Settings > Graphics) and set the Font Size Multiplier for each font size.