These nouns all relate to different kinds of thoughts. They are similar, but each one can be used in slightly different situations.

Knowledge – noncount – This is what you learn. Grammar, for example, or how to cook, or who is the most popular singer. “My friend has a lot of knowledge of soccer. She can tell you every championship winner since 1893!”

Memory – noncount – This is the biological ability to store or recall information. “I have a good memory. I know what shirt I was wearing on May 23rd, 1999.”

Memory/memories – count – these are countable thoughts about events you took part in. “I have many memories of playing with my grandparents when I was a child.” They are usually positive, but are not always positive. “My memory of school is unpleasant. I hated class!” They sound quite specific or detailed.

Experience/experiences – count – These are countable thoughts, like memories, but they could be longer in duration, or perhaps more difficult. “I had good experiences on my trip to Canada.” They can also be negative. “My trip to the South Pole was a bad experience. Too cold!” These tend to describe longer events in less detail than memories does.

Experience – noncount – The memory or knowledge of doing work at a job. “I have a lot of experience with Photoshop. I have used it for years.”

Wish/wishes – count – Something you hope can come true in the future, but you don’t expect it to come true. “I wish I could win the lottery.”

Dream/dreams – count – the pictures while you sleep OR something you hope can come true in the future. “My dream last night was crazy. I was a horse inside a train!” With the second definition: “My dream is to learn English, so I came to Canada and started studying.”