The best evidence for what you are asking comes from amnesic patients. The most famous and most close to the condition you describe was patient H.M.
See below some extracts from wikipedia :
Molaison's general condition has been described as heavy anterograde
amnesia, as well as temporally graded retrograde amnesia (Smith &
Kosslyn, 2007).Since HM did not show any memory impairment before the
surgery, the removal of the medial temporal lobes can be held
responsible for his memory disorder. Consequently, the medial temporal
lobes can be assumed to be a major component involved in the formation
of semantic and episodic long-term memories
Despite his amnesic symptoms, Molaison performed quite normally in
tests of intellectual ability, indicating that some memory functions
(e.g., short-term stores, stores for words, phonemes, etc.) were not
impaired by the surgery (Smith & Kosslyn, 2007; Corkin, 2002).
However, for sentence-level language comprehension and production,
Molaison exhibited the same deficits and sparing as in memory (MacKay,
James, Taylor & Marian, 2007).
In addition to his intact working memory and intellectual abilities,
studies of Molaison's ability to acquire new motor skills demonstrated
preserved motor learning (Corkin, 2002). In a study conducted by
Milner in the early 1960s, Molaison acquired the new skill of drawing
a figure by looking at its reflection in a mirror (Corkin, 2002).
Experiments involving repetition priming underscored Molaison's
ability to acquire implicit (non-conscious) memories, in contrast to
his inability to acquire new explicit semantic and episodic memories