There is not enough context to interpret all the possible meanings of these sentences, Jack. However, as they stand:
1. He could go there. = it is possible or it was permissable for him to go there.
2. He can go there. = it is possible or permissible for him to go there.
2. He would go there. = it was his habit or it is his willfulness to go there.
3. He should go there. = it is a good idea for him to go there.
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