Hello, I would appreciate some help with this!

Step 1: Convert the starting alcohol into the ethyl ether (OEt).

Reagents (typical): EtI (or EtBr), base (e.g., NaH ), suitable solvent.

Outcome: ROH → ROEt (no change to the epoxide stereochemistry).
2) use carbanion from Grignard reagent to open the ring with correct sterochemistry
3) Conver alcohol so formed into desired ether by williamson's synthesis.

Thank you! Because one of the substituents, is cis-alkene, is it possible to use alkyne (HCtriplebondC-Na+) with water to form alkyne on wedge, then use H2 and lindlars catalyst to get cis-alkene?

yes you can take propynide ion in place of GR and then do reduction using Lindlar's catalyst to get cis- alkene