EU 34 to US: men's 2–2.5, women's 3.5–4
Shoe size chart · Nike & Jordan
In short
Nike and Jordan have no EU 34: it falls between EU 33.5 (US men's 2, women's 3.5) and EU 34.5 (US men's 2.5, women's 4). Between two sizes, go by foot length in the chart.
Whose chart
Nike's official chart; Jordan uses the same one. Other brands can differ by half a size — adidas, New Balance, HOKA and On each publish their own chart, and every sneaker page converts your size with its brand's chart.