..."Das würde ich auch gern wissen. "
Translation: I would like to know that as well.
Question: Is the German phrase as ambiguous as the English translation ?
i.e. " I would like to know that as well." could mean:
(A): I know this thing, but i'd also like to know that thing. Or it could mean:
(B) :Some people know this thing, and i too would like to know it.
If the German phrase is not as ambiguous as the English, then should i translate it as A or B ?
If A, then how should I write B in German? If B, then how should I write A in German?
Das würde ich gern wissen!
It really is not (very) ambiguous. Or, to put it differently, any ambiguity arises from the missing context. Any sentence that has das (or der or die) as its object cannot exist without context. The "das" needs to refer to something.
Most commonly, that would be a sentence within a conversation.
Hans: "Ich frage mich, ob Trump Alzheimer hat." (I wonder if Trump is suffering from Alzheimer's.) Peter: "Das würde ich auch gerne wissen!" or, synonymously: "Das frage ich mich auch!"
Now, in this example the sentence in question is a reply to someone else NOT knowing a certain thing. This is a very common pattern in German.
However, it could also be used differently:
Hans: "Jens weiß wirklich, wie man bei Frauen punktet." ("Jens really knows how to score with women.") Peter: "Das würde ich auch gerne wissen."
But that is a very unnatural use of the language. Much more common would be an answer like this:
Peter: "Das würde ich auch gerne können."
That highlights another problem with the sentence: "zu wissen" has a more restricted scope of meaning than "to know". It is (almost) exclusively used for specific bits of knowledge or information, but not for skills.
The english sentence "I know German." or even "I know how to speak German" cannot (easily) be translated using "wissen".
"Ich weiß Deutsch." No. Plain wrong. "Ich kann Deutsch." Colloquial, but kind of ok. "Ich weiß, wie man Deutsch spricht." Ok, but verrry strange. "Ich weiß Deutsch zu sprechen." Ok, but dated.
So, to finally answer your question:
Neither A nor B are good or, to the very least, plausible translations.
If we go back to the example with Trump, a good englisch translation would be: "That I would like to know, too." (Putting the emphasis on the question if Trump suffers from Alzheimer's.)
slamRN also provided a good version. But again, it is very context dependant.