I can't paste the longitude and latitude from the site in the properties of the marker
Perhaps this graphic will help
If the graphic is not helpful (just copy the Latitude and Longitude as indicated in green); please tell us more about what you are trying to do. Have you placed a Marker on your Map? Have you provided code to center the map on that location?
Yes I have done but when I use the site https://www.latlong.net to take the long and lat and paste them in the app inventor properties of the marker, it doesn't paste
Paste with the ctrl + V keys.
Maybe show somehow on the picture where you want to paste something. Perhaps we misunderstand each other.