Invalid bucket name s3 testdm Bucket name must match the regex a-zA-Z0-9 - 1 255

Question

I tried to view the content of my bucket but I am getting this error:

C:\Users\jino>aws s3 ls s3:\\testdm

Parameter validation failed:
Invalid bucket name "s3:\\testdm": Bucket name must match the regex "^[a-zA-Z0-9.\-_]{1,255}$"