The idea for the Whanganui op shop began when the organisation got a call from a resident who wanted to donate to them. When Orphans Aid went to view the items, the number of donations was "overwhelming".
"This was a large building filled to the gills with beautiful collectables and antiques, and it's really blown us away. We're very thankful", Müller said.
"We want to really honour the donor and the items."
She said the donor asked to remain anonymous because they wanted the focus to remain on Orphans Aid and raising funds to help children.
This donation kick-started the opening of the pop-up op shop, and the organisation hoped it would become a well-established permanent shop in the future.
The op shop will be the first business to occupy the newly built space, which sits behind Cactus Creme and opposite Farmers at 87 Victoria Ave, Müller said.
"We've turned an empty, partially unfinished space into what we think is a really cool shop. It's not even completely finished, there's no ceiling and even some of the drywall is still undone."
But Müller said there was enough there to make something out of it.
"It's like it's been waiting for us to show up," she said.
Orphans Aid started in 2004 when the founder of the organisation, Sue van Schreven, dedicated her life to helping children after she visited Romania and saw the many children abandoned by their families in hospitals.
"Her heart broke for them," Müller said.
Orphans Aid first created a new orphanage in Romania, then expanded to appeals in Russia where they worked alongside institutions and orphanages to introduce services such as music classes, camps and physiotherapy.
"All sorts of things that as a family you would do for your child, but in these institutions often they miss out on," Müller said.
Over time, this expanded to helping more than 2300 children overseas across Russia, India, Uganda and now Ukraine. The aim was to "help provide a fuller life, more opportunities and more care for those children", Müller said.
"Each location we work in is not a one size fits all. A lot of it is with the relationships with the partners we've got there."
Müller said the money raised at the op shop would help supplement the overseas appeals.
She said it was important to know that every dollar that Orphans Aid received would help change lives.
"There are over 150 million orphans in the world, so it's nice to be out doing something and becoming a part of the solution."
The store opening is at 11am on Wednesday.
Donations are welcome; to donate contact Pam Müller at pam@orphansaidinternational.org