Redirection: new WP site/host but same domain

Hello folks,

I am building a WordPress site for a client whose site ranking is already very good. It’s not in WordPress, but within the site is a link to her WordPress.com blog.

While the domain will stay the same – I’ve already imported the blog posts, I don’t know what to do about redirecting the links to the old pages (all ending in .htm) to the new pages.

Where do I have to do the redirect? I’ve searched and searched, but can’t quite figure it out. It’s not a 301 redirect, as the domain isn’t changing, right? And it’s not moving a blog, as such (there were only 33 posts).

Old site is: https://straightforwardcoaching.com
Development site is: https://straightforwardcoaching.com.gridhosted.co.uk/ (this is a temp url and the gridhosted bit will drop out when we go live)

An example is that this page: https://straightforwardcoaching.com/clairebradford.htm will now be this page: https://straightforwardcoaching.com/clairebradford/

Thanks in advance for any help you can offer.