Did you follow the directions I gave in 2 posts now? You MUST allow Linux to use the microphone!! If you do not do these to allow Linux to use the microphone it will not work in Linux. Are you reading the links I have provided/looked up?

Once you give it the permissions to use the microphone you may have to try different settings for the input/microphone in audacity to get the one that will work for you. That is why I had posted this as well above: Audacity Manual

So your saying that its linux that cant read the microphone and not Audacity right?
If this is correct then I must add that linux OSs are regarded as plug and play (unlike windows) and no action needed

The issue is the Linux you have is running inside a container like a virtual machine. You have to give permissions to the container to allow it to see the microphone. The linux operating system as well as Audacity when you launch it are isolated from your main operating system. You need to grant permission to Linux to use the microphone controlled by your real OS Chrome.

In your case your OS is chrome NOT linux.

This bit you put in your signature:
Needs to be stated and seen as: Using Debian Linux in a container on ChromeOS via developer option. It is NOT the same as running Linux as a main operating system in the way it works and the way it would see hardware.

I have opened the setting up, but there is no where that it says a linux tab
https://ibb.co/gthxpzH

In settings go down to "Advanced" and hit that. Then go down to Developers and you will see Linux Development Environment, hit that. 6 lines down you will see "Allow Linux to access your microphone", turn it on. And now Linux can use the mic.

I know it is there as I just turned it on in my Chromebook.

EDIT: I installed audacity and set up the microphone per the steps above. It works like a charm, I was able to use the defaults and record my voice without issue and even export it as mp3 file. It will appear in your files folder under the Linux Files section.

I urge you to read the manual (from within audacity you can click a link to open online version) so you know how to set up the recording. To make it easy: Audacity Manual

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I managed to find some time for it and I managed to turn my recorder on for linux in the chromebook setting thanks!

I had a brief go at a record, yes it dose record sound that I input in. But it will only start the recording at the end of the track as it wont allow me to select it to record from the begining or somewhere in the middle. I have had a look at the manual and looked at the topic for recording but I can not find any thing in it for it hear though