A double slit has two slits, each 0.040 mm wide, with a distance of 0.200 mm between their centres…

Step 1. The fringe width. $\beta = \dfrac{\lambda D}{d} = \dfrac{550 \times 10^{-9}\ \text{m} \times 1.0\ \text{m}}{0.200 \times 10^{-3}\ \text{m}} = 2.75\ \text{mm}$.

Step 2. The central maximum. $w = \dfrac{2\lambda D}{a} = \dfrac{2 \times 550 \times 10^{-9}\ \text{m} \times 1.0\ \text{m}}{0.040 \times 10^{-3}\ \text{m}} = 27.5\ \text{mm}$.

Step 3. The ratio. $\dfrac{d}{a} = \dfrac{0.200}{0.040} = 5$. Also $\dfrac{w}{\beta} = \dfrac{27.5}{2.75} = 10$ fringe widths.

Step 4. The bright fringes. The orders with $|m| < 5$ are $0, \pm1, \pm2, \pm3, \pm4$. That is $2 \times 5 - 1 = 9$ bright fringes.

Step 5. The missing order. The order $m = 5$ falls on the first dark place of the diffraction pattern, which is the edge of the central maximum.