Ok, so you could just run certbot on windows and skip docker completely?
Getting and using your certificate via Let's Encrypt involves the following process:
1 - Order the certificate via ACME (using an ACME compatible tool like certbot)
2 - Validate your domain control via http or DNS (server a specific http response on that domain, or add a specific TXT record to that domains DNS). If http validation will be difficult, use DNS validation instead.
3 - Fetch your certificate and optionally convert it to the format you need
4 - Apply your certificate to the service you need it for
Steps 1-3 are performed using your ACME client (certbot or others).
Step 4 may involve your acme client deployment hooks/tasks or may be something you do manually or script.
Does Spring supported pkcs12 cert containers? if so, you could also just use win-acme or Certify The Web (which is a GUI) to get your cert as a PFX file (same as a .p12 file).
I know it feels like nobody is giving you a clear answer to your question but it's really broad topic. Getting a certificate and using it are two different things and both can be quite complicated.
Start by learning how to get your certificate using the ACME client of your choice, then look at how to apply/use it.