Can't accept $null

Ok so lets break apart whats happening :

New-ADUser -Name "BoB Glen" -GivenName "BoB"-Surname "Glen" -DisplayName "2003487" $secpasswd = ConvertTo-SecureString -String "pa$$word1" -AsPlainText -Force -AccountPassword $secpsswd -Enabled $true -Path "OU=Public,DC=Company,DC=epl,DC=local" 

The symbol ` is a escape character in powershell. An example of how to use it would be :

write-output " `" " 

this would output : " instead of the and error : missing the terminator which would be thrown is I did " " ". you can also use it to split long commands into multiable lines like

Get-Alias` -name "%" 

In the Command you are trying to use a -whatever is a parameter and the very next thing after it as the value you are submitting to that parameter

-parameter Value 

Also in powershell the $ is a variable.

$Hello = "World" 

The current issue you are having is you are calling a command and then try to create a variable in the middle of the command, as well as starting the command with a escape key and ending it with a escape key (unless its part of a larger command that you are splitting into new lines)

You can surround a value with parentheses like : (new command here)

A working command would look like this :

New-ADUser -Name "BoB Glen" -GivenName "BoB"-Surname "Glen" -DisplayName "2003487"` -AccountPassword (ConvertTo-SecureString -String 'pa$$word1' -AsPlainText -Force)` -Enabled $true -Path "OU=Public,DC=Company,DC=epl,DC=local" 

You will notice that the variable $secpasswd is removed, the command ConvertTo-SecureString is inside parenthesis () the first and last escape characters ` removed, added escape characters to new lines in the command to make it visually more understandable and finally put single quotes around the word pa$$word because double quotes will try and read $ as a variable, while single quotes are read literally.