Where is the multication sign on the apple keyboard

How to access symbols from macOS:

1) Open System Preferences > Keyboard and select the "Input Sources" tab. Then click the "Show in menu bar" option.

2) Now a new icon is in your menu bar. Clicking it show this:

3) Select "Show Emojis and Symbols" to see this tool ("Math Symbols" selected):

4) Once you add a symbol to your Favorites in the left-hand pane, you can drag it into a formula in any Apple App and most third-party apps.:

4 × 5 = 20

⚠️ NOTE: Some apps override that function. With MS Word for example, you need to use Word's "insert Symbol" function.

Here is Apple's Support document regarding inserting symbols:

Use emoji and symbols on Mac - Apple Support

Most apps use the asterisk. [Shift] 8

Perhaps I don’t understand your question … ?

Edit to add: Or are you asking how to enter unicode characters?

–> x

😉