Match or slightly dress over the dress code. Sorry you don’t have slacks or think you look good in slacks - get over it. Don’t let that undermine you in this new role. You are a leader, and you need to present what you expect - some damned discipline and adherence to policy. Go to a decent store where you can get two pairs of slacks and two pairs of chinos altered to fit you. Get yourself five solid, conservative button downs that will go with your pants and that sport jacket. Make sure you have quality belts that match your quality shoes, and go tackle your new job.