three or four days
Used to give an approximate number of days, similar to 'a few days' but explicitly between three and four.
I'm going on a trip for about three or four days.
Please take this medicine for three or four days in a row.
Compound of 三 (three), 四 (four), and 日 (day). The reading さんよっか is a contraction of さん (three) and よっか (four days), reflecting a common pattern for approximate day counts.