julia> conda activate juliaenv
ERROR: syntax: extra token "activate" after end of expression
Julia doesn’t use conda, or anaconda, so this doesn’t apply in any of its prompts. Julia has its own package manager, and Pkg prompt for it. You can use Julia without (conda or those) other package managers, that’s the default. Depending on what you want to do, you can use conda with PythonCall.jl (or directly with CondaPkg.jl), but not in that way, nor that exact command.
C:/ProgramData/anaconda3/Scripts/activate is just a path to a file, and doesn’t belong in Julia’s, or any REPL, even Python’s. It’s very likely you want to run it, then from the shell, or what you would call command-line, console in Windows. And I guess the same for your conda command.
I do understand that these are not julia commands - my question is when you start the Julia REPL from within VSCode (after having selected a specific conda environment), why do these activation commands get sent to the REPL at all?