It is late in night and I am so tired. I don't think I can get up early tomorrow morning, so I am writing a short message on a paper. Although the message is to be read by my little sister, I want to make use of this opportunity to learn and improve my English. Here is what I am writing:
"MewMew, I have written down the destination address on the envelope on your desk, but I can't find any postage stamps. Can you buy some for me? Please put a new Christmas card and our letters into the envelope."
Are there any grammatical mistakes in the message?