how many; how many pieces
Used to ask about the number of small, countable objects. The counter 個 is general and can be used for many items when a specific counter is not required.
How many apples are there?
How many oranges are there in the box?
この箱の中にボールが何個入っていますか。
How many balls are in this box?
I ended up eating quite a few cookies.
Please buy a few apples.
いくつ is a casual, general way to ask 'how many' without specifying a counter, while 何個 explicitly uses the counter 個 for small, discrete objects.
Standard kanji spelling for counting small objects.
Alternate kanji form using 箇; less common than 何個.
Combination of interrogative prefix 何 (なん, 'what') and counter 個 (こ, 'individual item').